Animals & Heatwaves: Not Just a Normal Summer

By Dr Chris Wacker, UNE Discovery

“It’s soooooo hot!”
Heatwaves have been in the news a lot lately, and no doubt also in your house and under your skin. In Armidale, where UNE Discovery is based, we are experiencing weeks of 33+ °C! OK, so that may not seem hot from where you are sitting and sticking to the chair, but it is for us! Like much of Eastern Australia, we are in the midst of yet another heatwave. If 33 °C is a heatwave for us, but just a normal Summer for you, what actually defines a heatwave? Are we, in Armidale, just melting snowflakes when we complain about the heat?

What are heatwaves and how are they different to a normal Australian Summer?
As you would expect, Australian summers are always a bit on the warmer side. And you often see folks on social media stating that “this is just Summer in Australia, it was hotter than this when we were kids!” Is this true? Possibly. But that’s not what a heatwave is. Thanks to the Scientists at Australia’s Bureau of Meteorology, we have a robust definition of the word ‘heatwave’. A heatwave is when both the maximum and minimum temperatures are higher than normal over three or more days. The second part of that, the part about the minimum temperatures, is very important because it means the environment doesn’t get a chance to cool down as much overnight. In other words, we get little to no relief from the heat.

Australia’s climate change: temperatures have risen, and continue to rise, both on the land and in the sea. Image: Bureau of Meteorology

Are heatwaves related to climate change?
We have always had heatwaves, that much is true, but they are getting more severe, with higher maximum and minimum temperatures, and the periods of these high temperatures are longer and more frequent. Some areas are also worse off than others. Climate change data predict that the Australian arid-zone will be one of the areas most affected by rising temperatures and will experience a pronounced reduction in annual rainfall. The area composing the arid-zone is predicted to expand and endure an increased frequency of heat waves and drought. Australian animals are extremely well-adapted to their environment and the current temperature cycles, and it is these highly adapted states which may make them particularly vulnerable to additional climate challenges.

The spinifex hopping mouse: a native Australian rodent and a master of living in hot, dry places. Photo credit: australiannature.com, Pavel German

What happens to Australian wildlife during heatwaves?
Are there any adaptations that Australian wildlife have that can help them survive heatwaves? Aren’t they already adapted to the heat? How does a heatwave change that? Let’s look at some examples of well-adapted Australian animals.

One mammalian group that is particularly well-adapted to the heat and aridity are the Australian native rodents due to specialised osmoregulation, so they need very little water, and a flexible diet. While 24 native rodent species inhabit the arid-zone, there is a paucity of information regarding their basic thermal biology, how they cope with temperatures, and how they will react when/ if the predicted increase in heat wave frequency, duration and intensity occurs. 

The now endangered spectacled flying fox. Photo credit: the Australian Museum

While some arid-zone bats, such as the inland freetail bat, can tolerate multiple days of 44 degrees and protect themselves from dangerous water loss by letting their body temperatures rise, other bat species don’t fare as well. In 2018, in Northern Queensland, 23,000 spectacled flying-foxes (almost a third of the species) were killed during a heatwave where the temperature exceeded 42 °C and lasted for multiple days.

The native zebra finch. Photo credit: ebird, Chris Wiley

The zebra finch, a small desert bird, like many animals avoids or limits its activity during the hottest part of the day. The particularly interesting thing about this little bird though is that it can pre-empt when it will be hot and feeds and drinks in preparation. Birds that have just been through one heatwave are better prepared for the next bout of very hot weather.

A dish of shaded, fresh, clean water with lots of rocks so small animals won’t drown. Photo credit: Greensourcedfw.org, Marshall Hinsley

What can you do for our wildlife?
While the future of our beautiful planet can often seem bleak, it’s always best to focus on the positive things we as individuals can do:

  • Plant trees and bushes (preferably native, if possible) in your yards and gardens and give animals a refuge. This will also keep your little patch of earth a bit cooler.
  • Provide plenty of clean, fresh water for animals to drink in your yards and garden. Keep it out of the sun to keep it cool. Place a brick or similar both inside and beside the dish so small animals can get in and out.
  • If you see animals such as kangaroos lounging under a tree in the heat of the day (it’s best to leave wildlife alone at any time), always leave them alone to rest.
  • If you see a stressed animal report it to your local WIRES group. Different types of animals will show their stress in different ways but most will appear lethargic or be acting unusually placid.

References:

Bondarenco, A., Körtner, G., and Geiser, F. (2014) Hot bats: extreme thermal tolerance in a desert heat wave. Naturwissenschaften, 101:679-685

Cooper, C.E., Hurley, L.L., Deviche, P., and Griffith, S.C. (2000) Physiological responses of wild zebra finches (Taeniopygia guttata) to heatwaves, Journal of Experimental Biology, 223 (12) jeb225524.

Vale, C.G. and Brito, J.C. (2015) Desert-adapted species are vulnerable to climate change: Insights from the warmest region on Earth. Global Ecology and Conservation, 4:369-379

Van Dyck, S. and Strahan, R. (2008) The Mammals of Australia. Reed New Holland, Melbourne.